PDF AD831 Data sheet ( Hoja de datos )

Número de pieza	AD831
Descripción	Low Distortion Mixer
Fabricantes	Analog Devices
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No Preview Available ! Low Distortion Mixer AD831 FEATURES Doubly Balanced Mixer Low Distortion +24 dBm Third Order Intercept (IP3) +10 dBm 1 dB Compression Point Low LO Drive Required: –10 dBm Bandwidth 500 MHz RF and LO Input Bandwidths 250 MHz Differential Current IF Output DC to >200 MHz Single-Ended Voltage IF Output Single- or Dual-Supply Operation DC Coupled Using Dual Supplies All Ports May Be DC Coupled No Lower Frequency Limit—Operation to DC User-Programmable Power Consumption APPLICATIONS High Performance RF/IF Mixer Direct to Baseband Conversion Image-Reject Mixers I/Q Modulators and Demodulators PRODUCT DESCRIPTION The AD831 is a low distortion, wide dynamic range, monolithic mixer for use in such applications as RF to IF downconversion in HF and VHF receivers, the second mixer in DMR base sta- tions, direct-to-baseband conversion, quadrature modulation and demodulation, and doppler shift detection in ultrasound imaging applications. The mixer includes an LO driver and a low noise output amplifier and provides both user-programmable power consumption and third order intercept point. The AD831 provides a +24 dBm third order intercept point for –10 dBm LO power, thus improving system performance and reducing system cost compared to passive mixers, by eliminating the need for a high power LO driver and its attendant shielding and isolation problems. The RF, IF, and LO ports may be dc or ac coupled when the mixer is operating from ±5 V supplies or ac coupled when oper- ating from a single-supply of 9 V minimum. The mixer operates with RF and LO inputs as high as 500 MHz. The mixer’s IF output is available as either a differential current output or a single-ended voltage output. The differential output is from a pair of open collectors and may be ac coupled via a trans- former or capacitor to provide a 250 MHz output bandwidth. In downconversion applications, a single capacitor connected across these outputs implements a low-pass filter to reduce harmonics directly at the mixer core, simplifying output filtering. When REV. C Information furnished by Analog Devices is believed to be accurate and reliable. However, no responsibility is assumed by Analog Devices for its use, nor for any infringements of patents or other rights of third parties that may result from its use. No license is granted by implication or oth- erwise under any patent or patent rights of Analog Devices.Trademarks and registered trademarks are the property of their respective companies. FUNCTIONAL BLOCK DIAGRAM �� �� �� �� �� �� �� � �� �� �� �� �� �� �� �� � �� building a quadrature-amplitude modulator or image reject mixer, the differential current outputs of two AD831s may be summed by connecting them together. An integral low noise amplifier provides a single-ended voltage output and can drive such low impedance loads as filters, 50  amplifier inputs, and A/D converters. Its small signal bandwidth exceeds 200 MHz. A single resistor connected between pins OUT and FB sets its gain. The amplifier’s low dc offset allows its use in such direct-coupled applications as direct-to-baseband conversion and quadrature-amplitude demodulation. The mixer’s SSB noise figure is 10.3 dB at 70 MHz using its output amplifier and optimum source impedance. Unlike passive mixers, the AD831 has no insertion loss and does not require an external diplexer or passive termination. A programmable-bias feature allows the user to reduce power consumption, with a reduction in the 1 dB compression point and third-order intercept.This permits a tradeoff between dynamic range and power consumption. For example, the AD831 may be used as a second mixer in cellular and two-way radio base stations at reduced power while still providing a substantial performance improvement over passive solutions. PRODUCT HIGHLIGHTS 1. –10 dBm LO Drive for a +24 dBm Output Referred Third Order Intercept Point 2. Single-Ended Voltage Output 3. High Port-to-Port Isolation 4. No Insertion Loss 5. Single- or Dual-Supply Operation 6. 10.3 dB Noise Figure One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A. Tel: 781/329-4700 www.analog.com Fax: 781/326-8703 © 2003 Analog Devices, Inc. All rights reserved. 1 page AD831–Typical Performance Characteristics �� 65 �� 64 �� 63 �� 62 �� 61 � � �� �� TPC 1.Third Order Intercept vs. Frequency, IF Held Constant at 10.7 MHz �� 60 10 100 FREQUENCY (MHz) 1000 TPC 4. Second Order Intercept vs. Frequency 80 70 60 50 40 30 20 10 0 10 100 1000 FREQUENCY (MHz) TPC 2. IF-to-RF Isolation vs. Frequency 90 80 70 60 50 40 30 20 10 0 10 100 1000 FREQUENCY (MHz) TPC 5. LO-to-RF Isolation vs. Frequency 60 2 x LO – IF 50 3 x LO – IF 40 LO 30 20 10 0 10 100 1000 FREQUENCY (MHz) TPC 3. LO-to-IF Isolation vs. Frequency 80 3 x RF – IF 70 2 x RF – IF 60 50 RF – IF 40 3 x RF – IF 2 x RF – IF 30 RF – IF 20 10 0 10 100 1000 FREQUENCY (MHz) TPC 6. RF-to-IF Isolation vs. Frequency –4– REV. C 5 Page AD831 APPLICATIONS Careful component selection, circuit layout, power supply dc coupling, and shielding are needed to minimize the AD831’s susceptibility to interference from radio and TV stations, etc. In bench evaluation, we recommend placing all of the components in a shielded box and using feedthrough decoupling networks for the supply voltage. Circuit layout and construction are also critical, since stray capaci- tances and lead inductances can form resonant circuits and are a potential source of circuit peaking, oscillation, or both. Dual-Supply Operation Figure 9 shows the connections for dual-supply operation. Supplies may be as low as ±4.5 V but should be no higher than ±5.5 V, due to power dissipation. The RF input to the AD831 is shown connected by an impedance matching network for an assumed source impedance of 50 . TPC 15 shows the input impedance of the AD831 plotted vs. frequency. The input circuit can be modeled as a resistance in parallel with a capacitance. The 82 pF capacitors (CF) connected from IFN and IFP to VP provide a low-pass filter with a cutoff frequency of approximately 140 MHz in down-conversion appli- cations (see the Theory of Operation section for more details). The LO input is connected single-ended because the limiting amplifier provides a symmetric drive to the mixer. To minimize intermodulation distortion, connect pins OUT and VFB by the shortest possible path. The connections shown are for unity-gain operation. At LO frequencies less than 100 MHz, the AD831’s LO power may be as low as –20 dBm for satisfactory operation. Above 100 MHz, the specified LO power of –10 dBm must be used. �� �� �� �� �� �� �� �� �� � �� � �� �� �� �� �� �� �� � �� �� �� �� �� �� � �� �� �� �� �� �� �� � �� �� �� �� �� �� �� �� �� �� �� � �� �� �� �� �� �� �� �� �� �� Figure 9. Connections for ±5 V Dual-Supply Operation Showing Impedance Matching Network and Gain of 2 for Driving Reverse-Terminated IF Filter –10– REV. C 11 Page

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